Inflatable antenna



March 28, 1961 H. D. JUSTICE INFLATABLE ANTENNA 2 Sheets-Sheet 1 Filed April l0, 1959 IN V EN TOR.

WKN.

w w v March 28, 1961 H. D. JUSTICE INFLATABLE ANTENNA 2 sheets-sheet 2 Filed April l0, 1959 5m W- Il- IN VEN TOR.

HAI? o4 .D da: r/ BY TTONEYS United States INFLATABLE ANTENNA Filed Apr. 10, 1959, Ser. No. 805,547

12 Claims. (Cl. 343-872) This invention relates generally to antennas and more particularly to inflatable type antennas which may be transported conveniently from one location to another.

There are several inflatable (or collapsible) type antennas in the prior art. Some of these are airborne and some are for use in ground installations. Both types employ an inflatable balloon which, when inflated, provides the structural frame to hold the antenna portion of the apparatus in the proper shape and in the desired position. In some of these structures the reflector surface which forms the antenna consists of a metallic coating on the inner surface of the balloon and in other types the antenna portion is formed by a diaphragm type structure which is located within the balloon and has its perimeter attached to the inside surface of the balloon so that when the balloon is inflated the diaphragm is pulled into its desired operating shape.

There are certain difficulties connected with these structures. One of the more obvious ones is the tendency of the balloon to become distorted due to wind and other factors. This distortion, of course, results in some distortion of the reflecting surface of the antenna which is an undesirable characteristic. A further disadvantage of these structures lies in the fact that they are frequently used in climates which are quite cold with a resultingy problem of ice formation thereon. Due to the weight thereof, such ice formation can cause serious deformation of the shape of the antenna surface.

To make the balloon strong enough so that it will better retain its shape requires adding material thus adding to the weight of the balloon and making transportation from one location to another difficult and also making assembly and disassembly more dilcult. A further consequence of the use of increased material is a tendency for a balloon to become a little deformed due to its own weight. Thus, some of the effect of the added strength is lost due to the added weight.

An object of the present invention is to provide an inflatable type balloon which is stronger and lighter than previous inllatable type balloons.

Another object of the invention is to provide an inflatable type balloon which has a de-icing characteristic.

A further object of the invention is to provide an inflatable type antenna which has less distortion than inilatable antennas of comparable size and of greater weight.

A further aim of the invention is to improve inllatable type antennas generally.

In accordance with the invention there is provided a first flexible element coated with a reflecting metal and having the general shape of a moderately shallow dish, and a second flexible element also having the shape of a shallow dish and having its perimeter substantially the same as that of the first llexible element, both perimeters being substantially circular although other shapes can be employed. Means for sealing the perimeters of said dishes together and to a structurally supporting ring with the concave portions of the dishes facing each other is "atent O "ice provided. Between the two surfaces of the flexible elements is provided a webbing means which connects together the inner surfaces of said dish-like elements in a particular pattern to form a predetermined channel-like system between the flexible elements with the inner surfaces of the flexible elements and the webbing means forming the walls of the channels. Means are also provided for passing air through said predetermined channel-like system and includes a pressure valve to maintain the inflated structure at a desired pressure. Warm or hot air may be forced in one end of this channel-like system and allowed to escape through the pressure valve at the other end of the channel system thus providing heating within the balloon to prevent ice formation.

In accordance with a particular form of the invention the webbing may be arranged in the balloon (inflated antenna) in a spiral manner. Thus air forced into the balloon at the center of the spiral will travel through the spiral-like channel formed by the webbing and gradually work its way out to the outer perimeter of the balloon where the spiral channel terminates and where the pressure valve is located which controls the pressure of the balloon at that point. The balloon is thus continually supplied with hot air to prevent ice formation thereon.

In another form of the invention the webbing may be positioned radially. The radial sectors may terminate in a cylinder located at the center of the balloon, said cylinder being divided by diaphragm means into two cylindrical structures end-to-end. Alternate chambers of the balloon structure (a chamber being formed by adjacent radial webbing sectors) having openings leading into one of the cylinders and the other sectors having openings leading into the other half of the cylinder. Air is pumped into one of the cylinders and llows into alternate chambers and then to the adjacent chambers through an opening in the webbing wall and then back to the other cylinder and out a pressure valve provided therefor. Thus circulation of hot air is provided through the balloon to maintain the de-icing feature.

In accordance with a third form of the invention the webbing is positioned within the two flexible dish-shaped flexible members to form a series of parallel chambers within the balloon. Each sector of webbing has an aperture therein, but at the opposite end thereof with respect to the aperture of the next succeeding sector of webbing. Thus when air is forced into the balloon, it will traverse the entire length of each sector before it can escape into the next adjacent sector, thus providing for a llow of warm air throughout the entire inner volume of the balloon. The last sector is provided with an air pressure valve similar to that employed in the other embodiments set forth above.

These and other objects and features of the invention will be more fully understood from the following detailed description thereof when read in conjunction with the drawings, in which:

Figs. l and la respectively show a perspective View and a side View of a preferred form of the invention;

Figs. 2 and 2a respectively show a perspective view and a side view of another species of the invention;

Figs. 3 and 3a respectively show a perspective View and a side View of a third species of the invention; and

Fig. 4 shows a perspective view of an exploded portion of the structure of Fig. 2.

It is to be noted that corresponding elements in the various figures will be identified by similar reference characters although primed in succeeding figures.

Referring now to Fig. l there is shown a flexible element 10 which has the general shape of a shallow saucer and which is coated on its inner surface with a conductive metallic material 15 (see Fig. la). This structure 10 and 15 forms the reflecting surface of the antenna. It is to be noted that although the shape of the structure 10 has been characterized by the phrase shallow saucer it has, in actuality a much better defined shape. For example, it could have a parabolic shape, which is a common shape for an antenna deilector. Alternatively it could have other shapes in accordance with the particular result desired. Similarly, the flexible element 11 has been designated as having a saucer-like shape. However, the principal function of the flexible element 11 is to complete the enclosure to form a balloon and since it has no electrical characteristics, its shape is not too important and is determined by considerations of convenience and practicality. These considerations appear to be best met by having it shaped in the general shape of a shallow saucer. As can be seen from the drawing, the flexible elements and 11 have the same overall perimeter configuration. A ring 40 of a strong, rigid material is provided for the purpose of supporting the perimeters of the flexible elements 10 and 11. Bolts 42 and 43 (Fig. la) function to secure ring 40 to a hase 41 which may contain the transmitter and the receiver equipment and also support a feeding horn 44.

The webbing 12 is positioned between the flexible elements 11 and 10 and its edges are secured to the flexible elements 11 and 16 so as to provide a spiraling channel which begins at the center of the balloon and spirals outwardly toward the perimeter thereof until it terminates at the output tube 14. As can be seen from Fig. la, an air source 16 is provided to force air into the center of the spiral channel. The hot air circulates through the spiral and works its way to the output tube 14 and then to the air valve 17 which functions to permit the air to escape from the balloon at some predetermined rate, but not so fast that the air pressure in the balloon will drop below a minimum desired value. It can be seen that the webbing 12 not only functions to provide the spiraling path for the hot air to circulate through the balloon and heat it to prevent icing, but also provides a substantial amount of structural strength to the balloon. Due to this added strength it has been found that the total Weight of the balloon is less than prior art balloons of similar size and similar strength.

Additionally, the webbing 12 functions to maintain the desired shape of the reflector surface considerably more accurately than prior art inflatable type antenna structures.

It is to be noted that both of the flexible structures 10 and 11 must be of reasonably airtight material and should be sufliciently heavy and sufficiently durable to withstand the packing and unpacking and the elements of nature to which an inflatable balloon is subjected ordinarily.

Referring now to Fig. 2, there is shown a modification of the invention in which the flexible elements 20 and 21, the reflector surface and ring 46 correspond to the flexible elements 10 and 11, reflector surface 15, and ring 40 of Fig. l. The webbing 22 is arranged :in a radial manner from the centrally located cylinder 23. This centrally located cylinder 23 is divided into two cylinders, 23a and 231; (see Fig. 2a and Fig. 4) by a diaphragm 24. The air is pumped into the cylinder 23b from air source 26 of Fig. 2a. The exhausted air is supplied to an air valve 27 which permits a circulation of air through the balloon but maintains a suflicient pressure within the balloon in a manner similar to the action of air valve 17 of Fig. 1.

The manner in which the air flows through the inflatable balloon of Figs. 2 and 2a can best be understood byl reference to the structure of Fig. 4, which is an exploded view of the cylinder 23 of Fig. 2a and shows brokenaway portions of the radial webbing sectors identified by the reference character 22. It can be seen from Fig. 4 that apertures, such as apertures 28, are provided in every alternate sector of the cylinder 23b, which sectors are formed by the intersection of the cylinder 23b and the webbing sections 22'. Hot air is thus supplied to every alternate compartment formed by the radial webbing sections. Further, as shown in Fig. 2, every alternate webbing section has an aperture formed therein near its radial extreme to permit the warm air to circulate from the compartment at which it is supplied to an adjacent compartment. The air in said adjacent compartment is then permitted to flow back into the cylinder 23a (Fig. 4) via apertures 29 and thence to the pressure valve 27'. It is to be noted that the apertures 29 are located in the cylinder 23a in staggered relationship with the apertures 28 of the cylinder 23h'.

The material employed in the webbing 22 and in the flexible elements 20 and 21 of Fig. 2 should have the same characteristics as similar material employed in the structure of Fig. l.

Referring now to Figs. 3 and 3a, the webbing is positioned Withinfthe flexible reflector element 33 and the nonconductive reflector element 34 in parallel strips 47 `so as to provide a series of parallel channels within the balloon. As in the case of structures in Figs. l and 2, the edges of the webbing are secured to the flexible clements 33 and 34 to form a reasonably airtight compartment within the inflatable balloon. It should be noted at this point that it is not necessary that the webbing be completely airtight, but it should be sufficiently airtight to prevent an undue amount of air flow directly therethrough, since it is desirable that the air follow the channels in order to provide proper heating of the structure.

In each strip of webbing there is provided at one end thereof an aperture such as apertures 36. These apertures are provided to permit air to flow through the parallel channels in a predetermined manner. This predetermined manner being as follows.

The apertures in each succeeding web are positioned at opposite ends of the adjacent web such that air flow must necessarily travel substantially the entire length of each channel before it can be admitted to the next channel. This insures a more uniform heating of the antenna structure. The air source 37 is provided to provide air to one of the end channels of the balloon structure, and the air valve 38 is provided to exhaust the air at the other end channel of the balloon. As in the case of the structure of Figs. 1 and 2 the air valve 38 functions to permit escape of air in sufficient amounts to insure continued flow of hot air through the balloon, but at the same time insuring that the pressure within the balloon is maintained above a minimum level. A rigid ring 48 is provided to support the perimeters of the flexible elements 33 and 34.

The antennas and the feeding horns of Figs. 2 and 3 can be mounted to the transmitter receiver structure in the manner shown in Fig. 1.

It is to be noted that the forms of the invention herein shown and described are but preferred forms thereof, and that various changes may be made in the configuration of the envelope thereof and of the webbing without departing from the spirit or scope of the invention.

I claim:

1. An inflatable antenna comprising a first flexible dishshaped member having a metallic surface thereon, a second dish-shaped member, means for sealing the perimeters of said dish-shaped members together with the concave portions thereof facing each other, and webbing means for connecting together the inner surfaces of said dishshaped members to form a predetermined channel system with the inner surfaces of said dish-shaped members and the webbing forming the Walls of the channel system, and means for passing air through said predetermined channel system including prcssure valve means for maintaining a desired pressure within said inflatable antenna.

2. An inflatable antenna in accordance with claim l comprising a ring of rigid material disposed around and secured to the perimeters of said dish-shaped members, base supporting means, and means for securing said ring to said base supporting means.

3. An inflatable antenna in accordance with claim 2 comprising transmitter means, and means for directing the output signal of said transmitter means upon said metallic surface.

4. An inflatable antenna comprising a first flexible element having a dish-like shape and having a metallic reflecting surface thereon, a second flexible element having a dish-like shape, means for sealing the perimeters of said flexible elements together with the concave portions thereof facing each other, webbing means for connecting together the inner surfaces of said flexible elements to form a predetermined channel system within the first and second flexible elements with the inner surfaces of the flexible elements and the webbing forming the walls of the channel system, said webbing constructed and arranged to form said channel into a spiralling channel beginning near the center of said flexible elements and extending outwardly to the perimeters of said flexible elements, and means for passing air through said predetei-mined channel system including pressure valve means for maintaining a predetermined pressure within said inflatable antenna.

5. An inflatable antenna in accordance with claim 4 comprising a ring of rigid material disposed around and secured to the perimeters of said flexible elements, base supporting means, and means for securing said ring to said base supporting means.

6. An inflatable antenna in accordance with claim 5 comprising transmitter means, and means for directing the output signal of said transmitter means upon said metallic reflecting surface.

7. An inflatable antenna comprising a first flexible element having a dish-like shape and having a metallic reflecting surface thereon, a second flexible element having a dish-like shape, means for sealing the perimeters of said flexible elements together with the concave portions thereof facing each other, and webbing means for connecting together the inner surfaces of said flexible elements to form a predetermined channel system within the first and second flexible elements with the inner surfaces of the flexible elements and the webbing forming the walls of the channel system, said webbing means constructed and arranged into sections of webbing to form said channel system into a plurality of parallel channels in which adjacent channels are separated by a section of said webbing means, each of said sections of webbing means having an aperture at one end thereof connecting adjacent channels, said apertures being located alternately in opposite ends of adjacent sections of webbing to provide for air flow through substantially the entire length of each channel, means for introducing air into an end one of said channels, and means including pressure valve means for exhausting the air from the other end of said channel means and for maintaining a predetermined pressure within said inflatable antenna.

8. An inflatable antenna in accordance with claim 7 comprising a ring of rigid material disposed around and secured to the perimeters of said flexible elements, base supporting means, and means for securing said ring to said base supporting means.

9. An inflatable antenna in accordance with claim 8 comprising transmitter means, and means for directing the output signal of said transmitter means to said metallic reflecting surface.

10. An inflatable antenna comprising a first flexible element having a dish-like shape and having a metallic reilecting surface thereon, a second flexible element having a dish-like shape, means for sealing the perimeters of said flexible elements together with the concave portions thereof facing each other, webbing means for connecting together the inner surfaces of said flexible elements to form a predetermined channel system within the first and second flexible elements with the inner suru faces of the flexible elements and the webbing forming the walls of the channel system, said webbing means constructed and arranged into sections to form said channel system into a series of radial channels extending from an area near the center of said flexible elements and extending outward towards the perimeters of said flexible elements, alternate sections of said webbing means forming the alternate walls of said radial channels and containing apertures therein near the perimeters of said flexible means, first means positioned near the center of said flexible elements for introducing air into alternate ones of said Iradial channels second means positioned near the center of said flexible elements for exhausting air from said radial channels other than said alternate radial channels, said means for entry and exhaustion of air being sealed from each other except through said apertures in the walls of said channels, and pressure valve means for maintaining a predetermined pressure within said inflatable antenna.

11. An inflatable antenna in accordance with claim 10 comprising a ring of rigid material disposed around and secured to the perimeters of said flexible elements, base supporting means, and means for securing said ring to said base supporting means.

12. An inflatable antenna in accordance with claim 11 comprising transmitter means, and means for directing the output signal of said transmitter means to said metallic reflecting surface.

References Cited in the ille of this patent UNITED STATES PATENTS 674,427 Palencsar Mayl 21, 1901 2,396,684 Chadsey Mar, 19, 1946 2,755,216 Lemons July 17, 1956 2,888,675 Pratt et al May 26, 1959 2,913,726 Currie et al Nov. 17, 1959 OTHER REFERENCES Pub. I. Science Newsletter, January 18, 1958, page 37. 

